Xiaoping Yan

Head–Disk Lubricant Transfer and Deposition During Heat-Assisted Magnetic Recording Write Operations

Lubricant accumulation was found on the media surface the instant when the laser is turned OFF during heat-assisted magnetic recording write operations. By changing the write cycles, laser ON/OFF duration, media, and head temperatures, we find that this lubricant accumulation is related to the change in head-media temperatures. The observed lubricant deposition process is restricted to a short time window (1-2 μs) after the laser is turned OFF. An equilibrium model of thermal displacement due to evaporation and condensation processes is presented and used to discuss the effect of the head-media temperature changes on the lubricant accumulation. Possible solutions to minimize the lubricant transfer and deposition are discussed.

Atomistic Frictional Properties of the C(100)2x1-H Surface

Density functional theory- (DFT-) based ab initio calculations were used to investigate the surface-to-surface interaction and frictional behavior of two hydrogenated C(100) dimer surfaces. A monolayer of hydrogen atoms was applied to the fully relaxed C(100)2x1 surface having rows of C=C dimers with a bond length of 1.39 A. The obtained C(100)2x1-H surfaces (C–H bond length 1.15 A) were placed in a large vacuum space and translated toward each other. A cohesive state at a surface separation of 4.32 A that is stabilized by approximately 0.42 eV was observed. An increase in the charge separation in the surface dimer was calculated at this separation having a 0.04 e transfer from the hydrogen atom to the carbon atom. The Mayer bond orders were calculated for the C–C and C–H bonds and were found to be 0.962 and 0.947, respectively. σ C–H bonds did not change substantially from the fully separated state. A significant decrease in the electron density difference between the hydrogen atoms on opposite surfaces was seen and assigned to the effects of Pauli repulsion. The surfaces were translated relative to each other in the (100) plane, and the friction force was obtained as a function of slab spacing, which yielded a 0.157 coefficient of friction.

Lubricant for Probe-Based Ferroelectric Recording Devices

In a probe-based ferroelectric recording system a protective coating of lubricant provides low friction and a low wear rate as well as allows the continuous contact of the probe tip with the storage medium. SO5, a member of the commercially available electric connector lubricants polyphenyl ether (PPE), was experimentally proven effective as a lubricant in supporting this probe/media interface and has enabled the demonstration of the probe-based ferroelectric recording technology. The unique stability of SO5 lubricant in an electric field and in the presence of electrons makes this liquid particularly suitable for ferroelectric recording storage devices. A broad range of analytical techniques were used to identify this lubricant as a mixture of alkylated diphenyl ethers having varying molecular weight. A thin layer of this lubricant was uniformly coated on the probe media surface through a dip-lubing procedure. Its thermal stability and wettability was investigated in terms of the requirements for the successful application of this unique ferroelectric recording technology. The impact of this lubricant film on the read/write capability, durability and tribological performance was also explored.Copyright